ABB Relion 670 Series Technical Reference Manual page 235

1MRK 505 208-UEN B
Voltage
UL1
UL2
UL3
IEC05000016 V1 EN
Figure 112: Voltage used for the inverse time characteristic integration
Technical reference manual
Trip signal issuing requires that the overvoltage condition continues for at least the
user set time delay. This time delay is set by the parameter t1 and t2 for definite
time mode (DT) and by selected voltage level dependent time curves for the
inverse time mode (IDMT). If the START condition, with respect to the measured
voltage ceases during the delay time, and is not fulfilled again within a user defined
reset time (tReset1 and tReset2 for the definite time and tIReset1 and tIReset2 for
the inverse time) the corresponding START output is reset, after that the defined
reset time has elapsed. Here it should be noted that after leaving the hysteresis area,
the START condition must be fulfilled again and it is not sufficient for the signal to
only return back to the hysteresis area. The hysteresis value for each step is settable
(HystAbs2) to allow an high and accurate reset of the function. It should be noted
that for Two step overvoltage protection OV2PTOV the IDMT reset time is
constant and does not depend on the voltage fluctuations during the drop-off
period. However, there are three ways to reset the timer, either the timer is reset
instantaneously, or the timer value is frozen during the reset time, or the timer
value is linearly decreased during the reset time..
Section 7
Voltage protection
IDMT Voltage
Time
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